Long-Term Soil Productivity (LTSP) Study

The Long-Term Soil Productivity (LTSP) Study is a series of experiments established across the United States and Canada to better understand how soil productivity responds to disturbances of soil porosity (due to compaction) or soil organic matter (due to removal by timber removal or other means). The study is based on the principle that a location’s net primary productivity is controlled by physical, chemical, and biotic soil processes that are affected by management.

The study is designed with triplicate forest plots in each of the North American ecozones which are designated with various levels of organic matter removal ranging from undisturbed (for control) to all surface organic matter removed with bare soils exposed (which is beyond the disturbance level of most common forestry practices).

Studying soil productivity is important since, globally, soils store two times more carbon than the atmosphere and nearly three times that in all above ground biomass. This carbon stock can be mobilized by soil microbes and released to the atmosphere as climate active gasses like carbon dioxide, methane, and nitrous oxide. With this strong link between microbial metabolism in the soils and climate change it is important to better understand the microbial community and their expressed characteristics in both disturbed and undisturbed soils.

The PhD work of Aria Hahn is investigating these questions. Sampling has occurred at 6 of the 110 LTSP sites for whole gas samples and metagenomic and metatranscriptomic analysis. Initial results indicate changes in microbial community composition with disturbance were limited to the organic horizon, suggesting that any impacts of the disturbance on deeper horizons are unresolvable 13 years post-harvest. Further, initial correlation and network analysis suggests that disturbed microbial community members interact more with one another. This potentially reflects a resilience force that buffers the community against changes in community level metabolism.